JP6021395B2 - Liquid discharge head and liquid discharge head driving method - Google Patents

Description

  The present invention relates to a liquid discharge head that discharges liquid using a piezoelectric actuator, and a method for driving the liquid discharge head.

  In recent years, in inkjet recording, a technique for ejecting high-viscosity ink with a small amount of water has been studied in order to suppress deformation such as paper curling and cockling due to water of the ink. In ink jet recording, a phenomenon is known in which ink near the ejection port of a nozzle that has not ejected ink for a long period of time increases in viscosity and the ejection port becomes clogged, resulting in a decrease in ejection performance and ejection failure. This phenomenon is likely to occur when a high viscosity ink containing a large amount of coloring material per unit volume is used.

  One method for preventing clogging of the discharge port is so-called “meniscus vibration” in which the meniscus is minutely vibrated by an actuator and the thickened ink in the vicinity of the discharge port is stirred, which is disclosed in Patent Document 1 and Patent Document 2. Has been.

  Patent Document 1 discloses a technique in which a meniscus exposed to the outside of a discharge port is minutely vibrated at a specific cycle by an actuator. On the other hand, Patent Document 2 discloses a technique in which a meniscus adjusting means such as an electric syringe draws the meniscus into the discharge port by depressurizing the liquid chamber communicating with the discharge port, and then causes the meniscus to vibrate slightly. Yes.

Japanese Patent No. 036313297 JP 2009-148927 A

  In the technique disclosed in Patent Document 1, since the meniscus is vibrated while being exposed to the outside of the ejection port, there is a possibility that ink is ejected accidentally or ink is scattered. Therefore, only a minute vibration is given to the meniscus. Since high viscosity ink tends to thicken, it is difficult to reliably prevent clogging of the discharge port if the meniscus vibration is very small. In the technique disclosed in Patent Document 2, since the meniscus is vibrated while being drawn inside the discharge port, it is possible to give a large vibration to the meniscus. Therefore, the technique disclosed in Patent Document 2 has a higher effect of preventing clogging of the ejection port due to high-viscosity ink than the technique disclosed in Patent Document 1. However, in the technique disclosed in Patent Document 2, meniscus adjusting means is provided in the flow path connecting the ink tank and the recording head, in addition to the piezoelectric element for ejecting ink. Therefore, a mechanism for the meniscus adjusting means is required separately, the configuration is complicated, and the apparatus is enlarged.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid discharge head and a method for driving the liquid discharge head that can prevent clogging of the discharge port with a simple configuration when discharging high viscosity ink. .

  In order to achieve the above-described object, a liquid discharge head according to the present invention includes a discharge port that discharges ink, a liquid chamber that communicates with the discharge port, and a piezoelectric that generates energy for discharging liquid from the discharge port. An actuator, a drive unit that drives the piezoelectric actuator, and a control unit that controls the drive unit, the drive unit configured to discharge a liquid from the discharge port, or a meniscus. A second voltage pulse for causing the meniscus to vibrate in a state of being held in the liquid chamber to the piezoelectric actuator, and the control unit selects a driving unit for discharging the ink from the driving unit. The first voltage pulse is output to the selected drive unit, and the second voltage pulse is output to drive units other than the selected drive unit.

  In order to achieve the above-described object, a method for driving a liquid discharge head according to the present invention includes a discharge port for discharging a liquid, a liquid chamber communicating with the discharge port, and a liquid when a first voltage pulse is input. A piezoelectric actuator that operates to discharge, and when the second voltage pulse is input, operates to vibrate the meniscus while the meniscus is held in the liquid chamber; the first voltage pulse and the first voltage pulse; A first step of preparing a liquid discharge head having a drive unit that outputs two voltage pulses; and a drive unit that discharges the liquid from the drive unit. A second step for outputting the first voltage pulse, and a third step for outputting the second voltage pulse to a drive unit other than the selected drive unit in parallel with the second step. And, with a.

  According to the present invention, the meniscus can be vibrated while being held in the liquid chamber by the piezoelectric actuator for discharging ink and performing recording. Therefore, even if the meniscus is vibrated greatly, the liquid is not discharged, and it is possible to achieve effective recovery of clogging of the discharge port with a simple configuration. Therefore, when discharging high viscosity ink, it is possible to make clogging of the discharge port difficult to occur with a simple configuration.

1 is a diagram illustrating a configuration of a main part of an ink jet recording apparatus equipped with a liquid discharge head according to a first embodiment of the present invention. It is a figure which shows the structure of the liquid discharge head of Embodiment 1 of this invention. FIG. 3 is a block diagram illustrating an electrical control configuration of the liquid ejection head illustrated in FIG. 2. 3 is a graph showing a drive waveform of a voltage pulse used in the liquid ejection head shown in FIG. FIG. 4 is a diagram for explaining the behavior of an ink meniscus in the liquid ejection head shown in FIG. 2. It is sectional drawing which shows the structure of the other liquid discharge head which can apply this invention. It is sectional drawing which shows the structure of the liquid discharge head of Embodiment 2 of this invention. It is a graph which shows the drive waveform of the voltage pulse used with the liquid discharge head shown in FIG. FIG. 8 is a diagram for explaining the behavior of an ink meniscus in the liquid ejection head shown in FIG. 7. It is a graph which shows the drive waveform of the voltage pulse used with the liquid discharge head of Embodiment 3 of this invention. FIG. 10 is a diagram for explaining the behavior of an ink meniscus in a liquid ejection head according to a third embodiment of the present invention. It is sectional drawing which shows the structure of the liquid discharge head of Embodiment 4 of this invention. 13 is a graph showing a driving waveform of a voltage pulse used in the liquid ejection head shown in FIG. FIG. 13 is a diagram for describing the behavior of an ink meniscus in the liquid ejection head illustrated in FIG. 12. FIG. 13 is a diagram for explaining another form of the liquid ejection head shown in FIG. 12. It is a graph which shows the drive waveform of the voltage pulse with respect to the nozzle which is used with the liquid discharge head of Embodiment 5 of this invention. It is a graph which shows the drive waveform of the voltage pulse with respect to the nozzle which is used with the liquid discharge head of Embodiment 5 of this invention, and does not discharge. It is a figure for demonstrating the behavior of the meniscus of the ink of the nozzle to discharge in the liquid discharge head of Embodiment 5 of this invention. It is a figure for demonstrating the behavior of the meniscus of an ink when the drive waveform of the voltage pulse shown in FIG.16 (b) is not input into the back piezoelectric element of the nozzle to discharge. FIG. 10 is a diagram for explaining the behavior of a meniscus of ink of a nozzle that does not eject in a liquid ejection head according to a fifth embodiment of the present invention.

(Embodiment 1)
FIG. 1 is a diagram illustrating a main configuration of an ink jet recording apparatus equipped with a liquid ejection head according to a first embodiment of the present invention. In the ink jet recording apparatus shown in FIG. 1, a recording medium 2 is placed on an endless belt-like conveyance belt 4 stretched around a conveyance roller 3, and the conveyance belt 4 is driven to convey the recording medium 2 in the conveyance direction (arrow). Scan (see X). The ink jet recording apparatus shown in FIG. 1 has four liquid discharge heads 1a to which ink is supplied from an ink tank 6 by a pump. Each liquid discharge head 1a corresponds to four colors of ink of yellow (Y), magenta (M), cyan (C), and black (Bk), and is juxtaposed in the conveyance direction of the recording medium 2. Full color recording is performed at high speed by ejecting ink of each color from each liquid ejection head 1a while transporting the recording medium 2 in the transport direction.

  FIG. 2 is a diagram illustrating a configuration of the liquid discharge head according to the present embodiment. FIG. 2A is a plan view of the liquid discharge head 1a as viewed from the ink discharge port side. FIG. 2B is a cross-sectional view taken along a cutting line AA shown in FIG. FIG. 3 is a block diagram showing an electrical control configuration of the liquid ejection head shown in FIG.

  As shown in FIG. 2A, the liquid discharge head 1a of the present embodiment has a discharge port plate 8 in which a plurality of discharge ports 7 are formed. The plurality of ejection openings 7 are arranged corresponding to the width of the recording medium 2. In the present embodiment, each discharge port 7 is a round hole having a diameter d (see FIG. 2A) of 17 μm. The discharge port plate 8 has a thickness t (see FIG. 2B) of 17 μm.

  A liquid chamber 9 communicates with each discharge port 7 individually. The dimensions of each liquid chamber 9 are a length L of 6000 μm, a width of 100 μm, and a height H of 200 μm (see FIG. 2B). Each liquid chamber 9 communicates with the common liquid chamber 10 through a narrowed portion 20 having a width of 30 μm.

A piezoelectric actuator 11 that generates energy for discharging liquid (ink) from the discharge port 7 is provided on the wall portion of the liquid chamber 9. In the present embodiment, the piezoelectric actuator 11 includes a bend mode type piezoelectric element 11a and a diaphragm 11b to which the piezoelectric element 11a is attached. The piezoelectric element 11a is driven by the drive unit 21 (see FIG. 3). The drive unit 21 supplies the piezoelectric element 11a with a voltage pulse P1 (first voltage pulse, see FIG. 4) for causing the piezoelectric actuator 11 to eject ink from the ejection port 7 according to the control of the control unit 31 (see FIG. 3). Output. The piezoelectric element 11a to which the voltage pulse P1 has been input causes the diaphragm 11b to be deformed inside the liquid chamber 9 (see arrow B in FIG. 2 (b)) and then returned to the initial state. Then, when the liquid chamber 9 contracts, ink is ejected from the ejection port 7 and recording is performed. The ink used in this embodiment is a clear ink (66% PEG 600, 33% pure water, 1% surfactant). The viscosity of the ink is 40 × 10 ⁻³ Pa · s (room temperature value), and the surface tension of the ink is 38 × 10 ⁻³ N / m (room temperature value).

  Next, the operation of the liquid ejection head 1a of this embodiment will be described. FIG. 4 is a graph showing drive waveforms of voltage pulses used in the liquid ejection head 1a of the present embodiment. In FIG. 4, the horizontal axis indicates time, and the vertical axis indicates the drive voltage input from the drive unit 21 to the piezoelectric element 11a.

  When recording information indicating recording contents is input from the main body of the inkjet recording apparatus to the control unit 31, the control unit 31 selects an ejection port for ejecting ink from the plurality of ejection ports 7 based on the recording information. Subsequently, the control unit 31 causes the driving unit 21 corresponding to the selected ejection port to perform a recording operation for outputting the voltage pulse P1 described above to the piezoelectric element 11a.

  In parallel with the above recording operation, the control unit 31 inputs the second voltage pulse to the piezoelectric element 11a to the drive unit 21 (drive unit other than the selected drive unit) corresponding to the ejection port that does not eject ink. The recovery operation of stirring the ink in the liquid chamber 9 is performed. The contents of the recovery operation and the behavior of the ink meniscus 12 associated with the recovery operation will be described below. FIG. 5 is a diagram for explaining the behavior of the ink meniscus 12 in the liquid discharge head according to the present embodiment.

  In the initial state before the recovery operation is performed, the ink meniscus 12 is positioned at the ejection port 7 (see FIG. 5A). In the first period t1 (see FIG. 4) of the recovery operation, the drive unit 21 applies a voltage lower than the reference voltage to the piezoelectric element 11a according to the control of the control unit 31. Then, the liquid chamber 9 expands as the vibration plate 11b is deformed into a shape warped to the outside of the liquid chamber 9. As the liquid chamber 9 expands, the meniscus 12 is drawn into the liquid chamber 9 from the discharge port 7 (see FIG. 5B).

  In the period t2 (see FIG. 4), in order to prevent the meniscus 12 from returning to the discharge port 7, the drive unit 21 applies a voltage lower than the voltage applied in the period t1 to the piezoelectric element 11a (FIG. 4). reference). Thereby, the liquid chamber 9 continues to expand gently, and the meniscus 12 is maintained in the liquid chamber 9 (see FIG. 5C).

  In the period t3 (see FIG. 4), the drive unit 21 continuously outputs the voltage pulse P2 to the piezoelectric element 11a a plurality of times (see FIG. 4). Each time the voltage pulse P2 is input to the piezoelectric element 11a, the diaphragm 11b reciprocates (vibrates) outside the liquid chamber 9 (see arrow C in FIG. 2B). The meniscus 12 vibrates with the reciprocating motion of the diaphragm 11b (see FIGS. 5C to 5E).

In the period t4 (see FIG. 4), in order to return the liquid chamber 9 to the original state, the liquid chamber 9 is contracted and the meniscus 12 is returned to the initial state. The meniscus 12 once protrudes to the outside of the discharge port 7 (see FIG. 5F) and then returns to the initial state (FIG. 5A).
As described above, in the present embodiment, a simple system can be realized by performing the ejection for performing the recording and the operation for performing the recovery by the piezoelectric actuator 11. Also, meniscus vibration with good responsiveness can be performed by performing the vibration operation of the meniscus not by a member such as a pump but by the actuator 11 located near the discharge port where the meniscus is formed.

  In the present embodiment, the recovery operation in which the drive unit 21 corresponding to the ejection port 7 that does not eject ink outputs the voltage pulse P2 is performed, and the drive unit 21 that corresponds to the ejection port 7 that ejects ink outputs the voltage pulse P1. It is performed in parallel with the recording operation. Therefore, the ink in the liquid chamber 9 communicating with the ejection port 7 that does not eject ink can be agitated during recording, so that the clogging of the ejection port 7 can be recovered even if there is a nozzle that does not perform the ejection operation for a long time. Can be made. Further, since the meniscus 12 can be vibrated while being held on the liquid chamber 9 side, liquid is not discharged even when the meniscus 12 is vibrated greatly, and the clogging of the discharge port 7 is effectively recovered. be able to. Therefore, it is possible to prevent clogging of the discharge port 7 when high-viscosity ink is discharged.

  Further, in this embodiment, the piezoelectric actuator 11 has a function of ejecting ink and a function of stirring the ink in the liquid chamber 9 (vibrating the meniscus 12). For this reason, since no new parts are required to prevent clogging of the ink at the ejection port 7, the cost performance is excellent.

  The liquid discharge head 1a of this embodiment is a so-called “edge shooter type head” in which the discharge port 7 is opened along the extending direction of the liquid chamber 9 (ink flow direction) as shown in FIG. is there. However, the present invention may be a so-called “side shooter type head” in which the discharge port 7 is opened in a direction orthogonal to the extending direction of the liquid chamber 9 as shown in FIG.

  In this embodiment, a bend mode piezoelectric element is used as the piezoelectric element 11a. However, a push mode, a share mode, or a Gould type piezoelectric element may be used.

(Embodiment 2)
FIG. 7 is a cross-sectional view showing the configuration of the liquid ejection head 1a of this embodiment. Constituent elements similar to those of the liquid ejection head 1a of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the liquid discharge head 1b of the present embodiment, as shown in FIG. 7, a liquid repellent layer 15 that repels ink is formed on the inner peripheral surface of the discharge port.

  Also in the present embodiment, the recovery operation is performed as in the first embodiment. Hereinafter, the recovery operation of the liquid ejection head 1a of the present embodiment and the behavior of the ink meniscus 12 associated with the recovery operation will be described. FIG. 8 is a graph showing a drive waveform of a voltage pulse used in the liquid ejection head 1b of this embodiment. In FIG. 8, the horizontal axis indicates time, and the vertical axis indicates the drive voltage input from the drive unit 21 to the piezoelectric element 11a. FIG. 9 is a diagram for explaining the behavior of the ink meniscus 12 in the liquid ejection head 1b of the present embodiment.

  In the initial state before the recovery operation is performed, since the liquid repellent layer 15 is formed on the inner peripheral surface of the discharge port 7, the meniscus 12 is held at the opening end of the discharge port 7 on the liquid chamber 9 side ( FIG. 9 (a)). First, the drive unit 21 outputs a trapezoidal voltage pulse P2 to the piezoelectric element 11a. When the voltage pulse P2 is input to the piezoelectric element 11a, the vibration plate 11b vibrates outside the liquid chamber 9. As a result, the meniscus 12 is pulled back into the liquid chamber and then returned to the original position (see FIGS. 9B and 9C). Then, the meniscus 12 is again drawn into the liquid chamber 9 by the next voltage pulse P2 (see FIG. 9D). In this embodiment, such vibration is repeated three times. The vibration of the meniscus 12 promotes the diffusion of the color material and the surfactant, and breaks the film formed of the color material and the surfactant.

  When the output of the third voltage pulse P2 is completed, the meniscus 12 moves to the ejection port 7 by the flow of ink from the common liquid chamber 10 side (see FIG. 9E), and eventually in FIG. 9F. Return to the initial state.

  In this embodiment, when a voltage pulse P2 having a period T (see FIG. 8) of 2 μs and an amplitude V (see FIG. 8) of 15 V is input to the piezoelectric element 11a, the meniscus 12 vibrates with an amplitude of about 14 μm. Due to this vibration, the nozzle could be recovered from clogging of the discharge port 7 due to thickening of the ink.

  In the present embodiment, a voltage pulse P2 having a period T of 2 μs, that is, a frequency of 50 kHz is used. The faster the meniscus 12 vibrates, the more effectively the nozzle can be recovered, so the frequency of the voltage pulse P2 is preferably several tens of kHz or more.

  According to the present embodiment, since the liquid repellent layer 15 is formed on the inner peripheral surface of the discharge port 7, even if a large vibration is applied to the meniscus 12 during the recovery operation, the meniscus 12 is mistaken from the discharge port 7. The phenomenon of discharging or scattering is less likely to occur.

(Embodiment 3)
The liquid ejection head of this embodiment will be described. The configuration of the liquid discharge head of the present embodiment is the same as that of the liquid discharge head 1b of the second embodiment. Hereinafter, differences from the liquid ejection head 1b of the second embodiment will be described in detail.

  FIG. 10 is a graph showing a drive waveform of a voltage pulse used in the liquid ejection head 1b of this embodiment. In FIG. 10, the horizontal axis represents time, and the vertical axis represents the drive voltage input from the drive unit 21 to the piezoelectric element 11 a. FIG. 11 is a diagram for explaining the behavior of the ink meniscus in the liquid discharge head 1b of this embodiment.

  In the initial state before the recovery operation is performed, since the liquid repellent layer 15 is formed on the inner peripheral surface of the discharge port 7, the meniscus 12 is an opening on the liquid chamber 9 side of the discharge port 7 as in the second embodiment. It is hold | maintained at the edge (refer Fig.11 (a)).

  In the initial period u1 (see FIG. 10) of the recovery operation, the drive unit 21 applies a voltage lower than the reference voltage to the piezoelectric element 11a to expand the liquid chamber 9. As a result, the meniscus 12 is further drawn into the interior (back) of the liquid chamber 9 (see FIG. 11B).

  In the period u2 (see FIG. 10) after the period u1, the drive unit 21 outputs the voltage pulse P2 to the piezoelectric element 11a three times in the same manner as in the second embodiment. As a result, the meniscus 12 vibrates (see FIGS. 11B to 11D).

  In a period u3 (see FIG. 10) after the period u2, in order to return the liquid chamber 9 to the original state, the liquid chamber 9 is contracted and the meniscus 12 is returned to the initial state. The meniscus 12 moves to the ejection port 7 by the flow of ink from the common liquid chamber 10 side (see FIG. 11E), and eventually returns to the initial state (see FIG. 11F).

  According to the present embodiment, the meniscus 12 is further pulled into the liquid chamber 9 from the state where the meniscus 12 is held at the opening end of the discharge port 7 on the liquid chamber 9 side, and is then vibrated. Therefore, the possibility of accidental ejection or ink scattering is further reduced, and the meniscus 12 can be vibrated with a larger amplitude. Therefore, the nozzle can be recovered more effectively from clogging of the discharge port 7 due to thickening of the ink.

(Embodiment 4)
FIG. 12 is a cross-sectional view showing the configuration of the liquid ejection head of this embodiment. The same components as those in the liquid ejection heads of the above-described embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the liquid ejection head 1c of the present embodiment, a front piezoelectric element 13 and a rear piezoelectric element 14 that is attached to the diaphragm 11b further away from the ejection port 7 than the front piezoelectric element 13 are disposed. In the present embodiment, the front piezoelectric element 13 and the rear piezoelectric element 14 are bend mode piezoelectric elements in the same manner as the piezoelectric element 11a described above. The front piezoelectric element 13 and the rear piezoelectric element 14 are driven by different drive units 21. A liquid repellent layer 15 is formed on the inner peripheral surface of the discharge port 7. The dimensions of each liquid chamber 9 are 9000 μm in length, and the width and height are the same as in the other embodiments. Each liquid chamber 9 communicates with the common liquid chamber 10 through a narrowed portion 20 having a width of 50 μm.

  Also in the present embodiment, the recovery operation is performed in parallel with the recording operation, as in the other embodiments. Hereinafter, the recovery operation of the liquid discharge head according to the present embodiment and the behavior of the ink meniscus associated with the recovery operation will be described. FIG. 13 is a graph showing drive waveforms of voltage pulses used in the liquid ejection head 1c of this embodiment. In FIG. 13, the horizontal axis represents time, and the vertical axis represents the drive voltage input to the front piezoelectric element 11 a and the rear piezoelectric element 14. FIG. 14 is a diagram for explaining the behavior of the ink meniscus in the liquid ejection head 1c of the present embodiment.

  In the initial state before the recovery operation is performed, since the liquid repellent layer 15 is formed on the inner peripheral surface of the discharge port 7, the meniscus 12 is held at the opening end of the discharge port 7 on the liquid chamber 9 side ( FIG. 14 (a)). First, the drive unit 21 (second drive unit) outputs a voltage pulse P3 (third voltage pulse) to the rear piezoelectric element 14. As a result, the liquid chamber 9 begins to expand, so that the meniscus 12 is further drawn into the liquid chamber 9 (see FIG. 14B). Subsequently, another drive unit 21 (first drive unit) outputs a voltage pulse P <b> 2 to the front piezoelectric element 13. Thereby, the meniscus 12 vibrates (see FIGS. 14B to 14D). When the output of the voltage pulse P3 whose pulse width is longer than the second voltage pulse is completed, the liquid chamber 9 contracts and returns to the original state, and the meniscus 12 returns to the initial state. At this time, the meniscus 12 moves to the ejection port 7 by the flow of ink from the common liquid chamber 10 side (see FIG. 14E), and eventually returns to the initial state (see FIG. 14F).

  In this embodiment, when a voltage pulse P2 having a period of 5 μs and an amplitude of 35 V is input to the front piezoelectric element 13, the meniscus 12 vibrates with an amplitude of about 25 μm. Due to this vibration, the nozzle could be recovered from clogging of the discharge port 7 due to thickening of the ink.

  According to the present embodiment, the operation of drawing the meniscus 12 and the operation of vibrating the meniscus 12 are performed by different piezoelectric elements. Therefore, the voltage pulse can be reduced compared to other embodiments using the same actuator. Thereby, the load on the piezoelectric element can be reduced and the life can be extended. Furthermore, since the size of each piezoelectric element can be reduced, the natural frequency of the piezoelectric element is increased, and a larger vibration can be applied to the ink in the liquid chamber 9.

  In this embodiment, bend mode piezoelectric elements are used as the front piezoelectric element 13 and the rear piezoelectric element 14, but push mode, shear mode, or Gould type piezoelectric elements may be used.

  In the present embodiment, the front piezoelectric element 13 and the rear piezoelectric element 14 are arranged in a row, but they may be arranged so as to be orthogonal to each other as shown in FIG.

(Embodiment 5)
The liquid ejection head of this embodiment will be described. The configuration of the liquid discharge head of this embodiment is the same as that of the liquid discharge head 1c of Embodiment 4 (see FIG. 12). The same components as those in the liquid ejection heads of the above-described embodiments are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the present embodiment, a description will be given of a configuration that can solve both the residual vibration generated in the ejected nozzle and the clogging of the ejection port 7 due to the thickening of the ink generated in the nozzle that is not ejected by a simple method.

  Also in the present embodiment, the recovery operation is performed in parallel with the recording operation, as in the other embodiments. Hereinafter, the recovery operation of the liquid discharge head according to the present embodiment and the behavior of the ink meniscus 12 associated with the recovery operation will be described with reference to FIGS. FIG. 16A is a diagram illustrating a driving waveform of a voltage pulse input to the front piezoelectric element 13 of the nozzle that performs ejection and recording, which is used in the liquid ejection head 1c of the present embodiment. FIG. 16B is a diagram illustrating a driving waveform of a voltage pulse input to the rear piezoelectric element 14 of the nozzle that performs ejection and recording. FIG. 17A is a diagram illustrating a drive waveform of a voltage pulse input to the front piezoelectric element 13 of the nozzle that does not discharge. FIG. 17B is a diagram illustrating a drive waveform of a voltage pulse input to the rear piezoelectric element 14 of the nozzle that does not discharge. 16 and 17, the horizontal axis represents time, and the vertical axis represents the drive voltage input to the front piezoelectric element 13 and the rear piezoelectric element 14. FIG. 18 is a view for explaining the behavior of the ink meniscus 12 of the nozzle to be ejected in the liquid ejection head 1c of the present embodiment. FIG. 19 is a diagram for explaining the behavior of the ink meniscus 12 when the drive waveform of the voltage pulse shown in FIG. 16B is not input to the rear piezoelectric element 14 of the ejecting nozzle. FIG. 20 is a diagram for explaining the behavior of the ink meniscus 12 of the nozzles that are not ejected in the liquid ejection head 1c of the present embodiment.

  The behavior of the ink meniscus 12 of the ejecting nozzle will be described with reference to FIGS. 16 and 18. The dotted line indicates the behavior of the meniscus 12 when the voltage pulse P5 (fifth voltage pulse) is not input.

  First, in order to eject ink, the drive unit 21 shown in FIG. 3 outputs a voltage pulse P4 (fourth voltage pulse) for ejecting ink to the front piezoelectric element 13 in FIG. 12 (FIG. 16A). )reference). Thereby, the ink droplet 16 is discharged from the discharge port 7 (refer FIG.18 (d)).

  Next, at the timing when the meniscus 12 is displaced toward the ejection port 7, the drive unit 21 shown in FIG. 3 starts outputting the voltage pulse P5 to the rear piezoelectric element 14 (see FIG. 16B). In the voltage pulse P5, the timing at which the liquid chamber 9 starts to expand is the timing at which the meniscus 12 is displaced toward the discharge port 7 (see FIG. 18 (f)). The timing at which the liquid chamber 9 is contracted is the timing at which the meniscus 12 moves backward (moves inside the liquid chamber 9) due to residual vibration (see FIG. 18G). Since the voltage pulse P5 expands and contracts the liquid chamber 9 so that the meniscus 12 moves in the direction opposite to the traveling direction of the meniscus 12, an effect of suppressing the residual vibration of the meniscus 12 is obtained.

  Here, when the voltage pulse P5 is not output to the rear piezoelectric element 14, the violent meniscus vibration after ejection is not easily cured, so that the drive frequency is greatly reduced (FIGS. 19D to 19H). reference).

  Next, the behavior of the ink meniscus 12 of the nozzles that do not discharge will be described with reference to FIGS. 17 and 20.

  In the initial state before the recovery operation is performed, since the liquid repellent layer 15 is formed on the inner peripheral surface of the discharge port 7, the meniscus 12 is held at the opening end of the discharge port 7 on the liquid chamber 9 side ( (See FIG. 20 (a)). Since no ejection is performed, no driving voltage is input to the front piezoelectric element 11a (see FIG. 17A). And the drive part 21 shown in FIG. 3 outputs the voltage pulse P5 to the back piezoelectric element 14 at the same timing as outputting to the nozzle to discharge. As a result, the meniscus 12 vibrates (see FIGS. 20B to 20D).

  According to this embodiment, the same voltage pulse is input to the rear piezoelectric element 14 of the nozzle to be ejected and the nozzle to be ejected, thereby suppressing the residual vibration of the ejected nozzle, and the ink generated at the nozzle that has not ejected. It is possible to prevent clogging of the discharge port 7 due to increase in viscosity. In the present embodiment, the voltage pulse input to the rear piezoelectric element 14 is the same for the nozzle to be ejected and the nozzle not to be ejected.

7 Discharge port 9 Liquid chamber 11 Piezoelectric actuator 11a Piezoelectric element 11b Diaphragm 21 Drive unit 31 Control unit

Claims (8)

A plurality of ejection ports for ejecting ink; a plurality of liquid chambers communicating with the ejection ports; a plurality of front piezoelectric actuators for generating energy for ejecting liquid from the ejection ports; A plurality of rear piezoelectric actuators provided apart from the discharge port, a plurality of driving units for driving the front piezoelectric actuator and the rear piezoelectric actuator, and a control unit for controlling the driving unit,
The driving unit applies a first voltage pulse for discharging liquid from the discharge port or a second voltage pulse for vibrating the meniscus in a state where the meniscus is held in the liquid chamber. And outputting a third voltage pulse having a pulse width longer than the second voltage pulse for holding the meniscus in the liquid chamber to the rear piezoelectric actuator,
Wherein the control unit selects a drive unit to eject the ink from the plurality of the drive unit, to output the first voltage pulse to the selected drive unit, the selected drive unit other than the driving part A liquid ejection head that outputs the second voltage pulse after outputting the third voltage pulse. The liquid discharge head according to claim 1 , wherein a liquid repellent layer is formed on an inner peripheral surface of the discharge port, and a meniscus is held in the liquid chamber. A method of driving a liquid discharge head,
When a first voltage pulse is input, a plurality of discharge ports for discharging liquid, a plurality of liquid chambers communicating with the discharge port, and a second voltage pulse are input. A plurality of front piezoelectric actuators that operate to vibrate the meniscus in a state where the meniscus is held in the liquid chamber, and the pulse width of the second piezoelectric actuator is greater than that of the front piezoelectric actuator. A plurality of rear piezoelectric actuators that operate to hold the meniscus in the liquid chamber when a third voltage pulse longer than the voltage pulse is input; the first voltage pulse; the second voltage pulse; A first step of preparing a liquid ejection head having a plurality of drive units for outputting the third voltage pulse;
A second step of selecting a drive unit for discharging the liquid from a plurality of the drive units, and outputting the first voltage pulse to the selected drive unit;
In parallel with the second step, the third step of outputting the second voltage pulse after outputting the third voltage pulse to a drive unit other than the selected drive unit, A method for driving a liquid discharge head. The second voltage pulse includes a voltage pulse for causing the piezoelectric actuator to draw the meniscus into the liquid chamber, and another voltage pulse for oscillating the meniscus in the liquid chamber that is continuous with the voltage pulse. The method for driving a liquid ejection head according to claim 3 , comprising: A plurality of ejection ports for ejecting ink; a plurality of liquid chambers communicating with the ejection ports; a plurality of front piezoelectric actuators for generating energy for ejecting liquid from the ejection ports; a plurality of rear piezoelectric actuators provided away from the discharge port, and a plurality of first driving units driving the plurality of the front piezoelectric actuator individually, the second drive for driving together a plurality of the rear piezoelectric actuator And a control unit that controls the first and second driving units,
A liquid repellent layer is formed on the inner peripheral surface of the discharge port,
The first driving unit outputs a first voltage pulse for discharging liquid from the discharge port to the front piezoelectric actuator,
Wherein the control unit selects the first drive unit to eject the ink from a plurality of the first drive unit, to output the first voltage pulse to the first driving unit selected,
The second driving unit is configured to vibrate the meniscus in a state where the meniscus of the liquid chamber corresponding to the first driving unit other than the selected first driving unit is held in the liquid chamber. A liquid ejection head for outputting a pulse to all the rear piezoelectric actuators. The second driving unit expands the liquid chamber by outputting the second voltage pulse at a timing when the meniscus of the liquid chamber corresponding to the selected first driving unit moves to the discharge port side. and deflating said fluid chamber by the meniscus of the liquid chamber to the first driving portion and the selected outputs said second voltage pulse at a timing to move to the inside of the liquid chamber, claim 5 The liquid discharge head described in 1. A method of driving a liquid discharge head,
A plurality of discharge ports in which a liquid repellent layer is formed on the inner peripheral surface for discharging the liquid, a plurality of liquid chambers communicating with the discharge port, and a liquid when the first voltage pulse is input A plurality of front piezoelectric actuators that operate, and the meniscus that is provided farther from the discharge port than the front piezoelectric actuator and does not discharge liquid when a second voltage pulse is input into the liquid chamber. the plurality of rear piezoelectric actuator which operates to vibrate the meniscus in the holding state, a plurality of first driving unit which outputs the first voltage pulse, a plurality of outputting the second voltage pulse A first step of preparing a liquid ejection head having two drive units;
A second step of selecting a first driving unit for discharging the liquid from the first driving unit, and outputting the first voltage pulse to the selected first driving unit;
A liquid ejection head driving method comprising: following the second step, a third step of outputting the second voltage pulse to all the second driving units. In the third step, the liquid chamber is expanded by outputting the second voltage pulse at a timing when the meniscus of the liquid chamber corresponding to the selected first driving unit moves to the discharge port side, and deflating said fluid chamber by the meniscus of the liquid chamber to the first driving portion and the selected outputs said second voltage pulse at a timing to move to the inside of the liquid chamber, in claim 7 A driving method of the liquid discharge head described.

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